GB2185641A

GB2185641A - Cable vibration dampener and method of installing

Info

Publication number: GB2185641A
Application number: GB08628780A
Authority: GB
Inventors: Thomas E Sherman
Original assignee: Preformed Line Products Co
Current assignee: Preformed Line Products Co
Priority date: 1985-12-03
Filing date: 1986-12-02
Publication date: 1987-07-22
Also published as: IN169112B; GB8628780D0; GB2185641B; DE3640919A1; MX160975A; AU6604186A; DE3640919C2; JPH0410291B2; JPS62163511A; ZA869140B; BR8605887A; AU573466B2; NZ218471A; US4620059A; CA1256524A

Description

GB 2 185 641 A 1

SPECIFICATION

Cable vibration dampener and method of installing 65 Background of the Invention

The subject invention is directed to a vibration dampener and a method of installing the same.

The invention is especially suited for use on electric power lines and will be described with particular 10 reference thereto; however, as will become apparent, the invention is capable of broader application and could be used on a variety of aerial cables, quywires and the like.

Under certain wind conditions, and especially when accompanied by icing, aerial electric power lines or cables are sometimes subjected to a phenomenon commonly called "galloping". Galloping is a lowfrequency, high amplitude motion of the lines. When it 80 becomes severe, it can cause damageto the electrical 20 conductors, the supporting structures and support hardware.

Asomewhat parallel phenomenon is known as aeolian vibration. This is a higher frequency, lower amplitude vibration than that generally associated 25 with galloping. As a smooth stream of air passes over a cylindrical shape, such as a power line, alternating vortices are formed which create alternating press ures thattend to movethe power line at right angles to 90 the direction of airflow. It is this mechanism which 30 causes aeolian vibration.

Aeolian vibration can, over a period of time, damage the system in somewhat the same manner as galloping. Consequently, there has been a constant and ongoing interest in developing methods and apparatusforsuppressing both galloping and aeolian vibrations.

A device has recently been developed which suppresses galloping and significantly reduces aeolian vibrations. The device comprises a nonmetallic 40 rod having a length in a range of approximately 10to 18feet. Each end of the rod has a multipleturn, helically configured gripping section designed to tightlyfit and grip a relatively narrow range of wire or cable diameters. The midsection of the rod between the helical end portions is generally straight.

In installing the device, the installerfirstwraps one helical end section into gripping relationship with the electrical cable. He then moves to the opposite end of the device and wraps the entire straight midsection of 50 the rod at leasttwice around the cable to produce a long, slow helixwrap. Thereafter, the second helically configured end section is wound tightly into gripping relationship withthe cable.

The long, slow helix wrapped midsection of the 55 device acts to vary the aerodynamic profile of the cable and increases the cables aerodynamic stability. When the total cable span has the devices applied thereto, cable galloping and aeolian vibration are eliminated or significantly reduced.

Devices of the type discussed have proven highly desirable forthe purposes described. However, one of the problernswith the devices has been certain A b 45 installation difficulties. Specifically, because of their significant length and relative flexibility, they are somewhat difficult to hold in position as the first gripping helix is wound in place on the cable. In add iti on, after the first end is insta I I edthe entire rod dangles and swings as the installer moves to the second end to complete the wrapping and the 70 attachment of the helically configured gripping section at that end. Since the installations are often made at substantial elevations using trolleys and personnel lift equipment, the dangling, swinging rod can present special problems and slows down the installation 75 process.

Brief Statement of the Invention

The subject invention provides an improvementto the general vibration dampener structure described above which overcomes the noted installation problems and allows the dampeners to be installed by an inventive method.

Specifically, in accordance with one aspect of the subject invention, the vibration dampener device comprises an elongated flexible rod having a general- 85 ly straight midsection of substantial length terminating in relatively short end sections. Each end section includes a cable gripping portion in the form of a multiple helix sized to tightly encircle and grip the cable on which the dampener is to be installed. Formed adjacent at least one end section is a support helix sized to freely encirclethe cable without substantial gripping. Preferably,the support helix is sized such thatwhen it is in position aboutthe cable the cable can slide relatively f reely therethrough.

In accordance with another aspect of the invention, there is provided a method of installing the improved dampener. The method generally includes grasping the dampener adjacentthe support helix and wrapping the support helix aboutthe cable at a first 100 location. Thereafter,the dampener is slid along the cable to bring the end furthestfrom the support helix to generally the first location. The cable gripping portion adjacentthat end is then wrapped aboutthe cable. Thereafter, the installer moves to a second 105 location adjacentthe support helix and wraps the midsection of the vibration dampener at leasttwice aboutthe cable and then wraps the cable gripping section adjacentthe support helix into cable gripping relationship about the cable.

Through the provision of the support helix, the installation of the dampener can be accomplished by a single person without having the dampener dangling or swinging from the cable. The use of the support helix maintains the dampener completely under 115 control at substantially all times during the installation process. In addition, support and control is provided without the necessity of resorting to a separate support structure or requiring additional installation personnel.

Accordingly, a primary object of the invention isthe provision of avibration dampener devicewhich is simplerto install than prior devices.

Afurtherobject is the provision of a dampener device of the general type described which includes The drawing(s) originally filed was (were) informal and the print here reproduced istaken from a laterfiled formal copy.

GB 2 185 641 A 2 an integrallyformed portion thatcan be used for supporting afree end ofthe device during installation.

Anotherobject isthe provision of a method of installing a vibration clampenerof thetype described 5 by a series of steps which allow the dampener to be maintained underthe control of a single installer at all times.

Brief Description of the Drawings

The aboveand otherobiec'z-j and advantageswill 10 become apparentfrom the fodowing description when read in conjunction with the accompanying drawings wherein:

Figure 1 is aside view of a vibration dampener formed in accordance with the preferred embodi- 15 ment; FIGURE 2 is an enlarged view of the left-hand end, or circled portion, of FIGURE 1; FIGURE 3 is a viewof approximatelythe left-hand half of a vibration dampener installed on an overhead 20 cable and including a series of small cross-sectional views show icing conditions resulting atvarious spaced locations with the vibration dampener in place; and FIGURES 4-6 showthesequence of steps used in 25 installing the vibration dampener of FIGURE 1.

Detailed Description of the Preferred Embodiment

Referring more particularly to the drawings wherein the showings are forthe purpose of illustrating a preferred embodiment of the invention only, and not forthe purpose of limiting same, FIGURE 1 shows the 95 overall arrangement of a vibration dampener or air flow spoiler comprising an elongated rod member 10 having a generally straight intermediate section 12 terminating in g ripping end portions 14 and 16. The 35 elongated rod member 10 could be formed from any 100 of a variety of different materials having suitable characteristics. In the subject embodiment, however, it is preferably formed from a non-metallic material such as polyvinyl chloride (PVC) plastic.

40 In the embodiment under consideration, the rod member 10 has a diameter of approximately one-half inch and an overall length of approrximatelyfourteen feet.These dimensions could, of course,vary some what. The central section 12 has a length of approx- 45 imately twelve feet.

Both of the gripping sections 14 and 16 have a helical configuration sizedto tightly encircle and grip the cable on which the dampener is to be installed.

The use of such helical gripping sections is well known 50 in the art. A variety of prior art patents described the use of such helixes andtheir design so asto properly grip and tightly hold on the cable or wire to which such appliances are to be installed. For example, U.S.

Patents 2,744,707,3,286,923, and 3,664,010 described 55 and illustrate the design and application of such 120 helical gripping portions.

FIGURE2 illustratesthe left-hand gripping section 16. As shown therein, the internal opendiameter I.D. is sizedso asto beslightly lessthan the outer diameter 60 of the cable or conductor on which the unitisto be installed.The outer diameter O.D. of the helical gripping portion does, as is apparent, depend on the I.D- and the diameter of the rod from which the dampener is formed.

65 Dampeners having the general characteristics thus 13G far described are known in the art. They have been applied by first wrapping one gripping end portion to the cable and then moving to their other end and wrapping the midsection 12 at leasttwice around the 70 cable to produce a long, slow helix configuration tightly engaged with the cable. Subsequeritto wrapping the midsection 12, the final gripping section 12 is applied.

FIGURE 3 shows approximately the left-hand half of 75 a dampener of the general type described attachedto a conductor or a cable 20. With the dampener in position, the combined dampener and cable present a constantly changing aerodynamic cross-section shown in the series of small figures associated with 80 FIGURE 3. The constantly varying cross-section tends to create airvortices at a variety of different points around the composite cable and dampener configuration. The varying locations of these vortices tend to suppress wind induced motions of the cable. Even 85 under icing conditions the resulting aerodynamic cross-section varies continuously in a mannerwhich suppresses wind induced motions. The small crosssectional views in FIGURE 3 also show a typical icing situation in which the resulting shapes are depicted by 90 the shaded areas. Even when icing takes place, non-uniform aerodynamic cross-sections remain.

As discussed earlier, one of the problems connected with installing these vibration dampeners has been the necessity of installing one end portion in gripping relationship with the cable and then moving the substantial distanceto the otherend for applying itto the cable. Normally, eithertwo installers mustwork jointly orthe spoiler dangles and swingsfrom the cable while the single installer moves to the other end.

In accordancewith the subject invention a mod[fication to the basic vibration dampener configuration is provided such that installation is greatly facilitated and can be performed bya single installer. Specifically, according to the subject invention, at least one of 105 the gripping end portions 14 or 16 includes an associated non- gripping support helixwhich can be used to support one end of the dampenerwhile permittingfree sliding of the dampeneralong the cable. Inthe embodiment under consideration, the 110 left-hand end portion of the dampeneris provided with a support helix portion 24which is located adjacentthe end of the dampener, preferably between the gripping end portion 16 andthe midsection 12. Support helix 24 has an internal diameter D (see 115 FIGURE 2) which is at least nearly as large and preferably slightly largerthan the outer diameter of the cable on which the dampener is to be installed. In any event, itshould be largerthan the helixes of the gripping portion and sized so that when it is applied to the cable itcloes not griptightly and the cable can slide freely therethrough. The support helix portion preferably makes at least onefull loop or, in otherwords, has one full pitch P, however itcould have more loops if desired so long as tight gripping of the cable does not 125 result.

In addition, the support helix and the helically formed gripping sections preferably have a common spiral, ie. left-hand or right-hand.

FIGURES 4-6 illustrate the preferred sequence of steps used in applying or installing a vibration I GB 2 185 641 A 3 dampener incorporating the support helix feature.

First, the installer grasps the vibration dampener adjacent the support helix 24 and applies the support helix to the cable 20 by wrapping it once aboutthe 5 cable, as shown in FIGURE 4. The end portion of the 70 dampener is thus supported by the Gable but can slide freely therealong since, as discussed, the support helix is sized so as not to tightly grip or grasp cable 20.

Thereafter the installer, while remaining at position A, 10 slides the dampener to the left to bring the gripping end portion 14 into location generally at position A.

The gripping end portion 14 is then wrapped aboutthe cable to firmly grip the cable and lockthe vibration dampener into position thereon. The opposite end of 15 the dampener is, of course, supported during this operation bythe support helix 24. The installerthen moves from position A to position B adjacent the gripping end portion 16. At position B he releases the support helix 24 and pulls on the clampenerto 20 eliminate drooping in the midsection and then wraps 85 the straight midsection 12 twice aboutthe cable 20 as shown in FIGURE 6. While remaining at position 13, the installer subsequently wraps gripping section 16 into the final gripping and engaging position to complete the installation.

If the dampener is pulled longitudinally immediate ly priorto and during the installation of gripping section 16, the support helix is stressed andtensioned in the nature of a spring. The support helix can thus function to keep the midsection of the dampener tightly engaged with the cable even during ambient temperature changes which might otherwise produce sagging due to differences in the coeff icients of thermal expansion of the cable and the dampener.

As is apparentfrom the foregoing, the dampener is 100 basically under complete control throughout the installation process. Furthermore, the installation can be performed by a single person withoutthe unattached end portion swinging free at any time.

Claims

The invention has been described with reference to 105 the preferred embodiment. Obviously, modifications and alterations will occurto those skilled in the art. It is intencledto include all such modifications and alterations insofar asthey come within the scope of the following claims orthe equivalents thereof. CLAIMS Havingthus described the invention, it is now claimed:

1. A device for dampening wind induced vibra- tions in aerial cables comprising: an elongated rod having a generally straight miclsection terminating in helically configured cable gripping sections sized so as to tightly g rip the aerial cable on which the device is to be used, and a support helix associated with at least 55 one of said gripping sections, said support helix comprising at least one complete spiral with an open inner diameter greaterthan the inner diameter of the helically configured gripping sections and at least approximately as great as the diameter of the cable on 60 whicl-tthe device isto be used.

2. The device of claim 1 wherein said support helix is located between said midsection and the associated gripping section.

3. The device of claim 1 wherein said elongated 65 rod is formed of a non-metallic material.

4. The device of claim 1 wherein said rod has a length greater than approximately ten feet.

5. The device of claim 1 wherein said support helix isa continuation of the associated gripping helix.

6. The device of claim 1 wherein each of said helical gripping sections are spira led in the same direction.

7. The device of claim 6 wherein said support helix is spiraled in the same direction as said helical gripping sections.

8. A method of installing on aerial cables a vibration dampener of the type comprising an elongated rod with a generally straight midsection terminating atfirstand second ends in cable gripping 80 helical sections and having at leastone non-gripping support helix adjacent the first end, said method comprising the steps of:

a) at a first location adjacent the cable, wrapping said support helix about the cable; b) while remaining generally at said first location, sliding said road along said cable to bring said second end generally to the first location; c) wrapping the cable gripping helical portion at the second end into gripping relationship with said 90 cable; d) wrapping the straight midsection of the rod around said cable and; thereafter, e) applying the cable gripping helical portion at the first end to said cable.

9. The method as defined in claim 8 wherein said straight midsection is wrapped at least twice around said cable.

10. The method as defined in claim 9 wherein said support helix is unwrapped from said cable priorto wrapping said straight midsection.

11. The method as defined in claim 8 including the step of movingto the first end of said rod priorto wrapping the straight midsection about said cable and applying the cable gripping helical portion to said cable.

12. The method as defined in claim 8 including the step of applying a substantial longitudinal force to the dampenerto. longitudinally tension said support helix priorto applying the cable gripping helical portion at 110 thefirstend.

Printed in the United Kingdom for Her Majesty's Stationery Office by the Tweeddale Press Group, 8991685, 7/87 18996. Published at the Patent Office, 25 Southampton Buildings, London WC2A 1AY, from which copies may be obtained.